Preparation method and application of tungsten-titanium alloy target material

Abstract

The invention discloses a preparation method and application of a tungsten-titanium alloy target material, and belongs to the technical field of target materials for diffusion barrier layers of integrated circuits. The prepared tungsten-titanium alloy target material is low in gas content and fine and uniform in grain size, a titanium-rich phase is uniformly distributed in a tungsten-rich phase, and the tungsten-titanium alloy target material has high density and high solid solubility. The preparation method comprises the following steps: carrying out high-energy ball milling and powder mixing on high-purity tungsten powder and titanium powder; performing cold isostatic pressing molding; performing microwave sintering; and carrying out solution treatment. The tungsten-titanium alloy target material prepared by the method can be applied to sputtering of a diffusion barrier layer of a large-scale integrated circuit.

Description

Technical Field

[0001] The invention discloses a preparation method and application of a tungsten-titanium alloy target material, and particularly relates to the technical field of target materials for diffusion barrier layers of integrated circuits. Background Art

[0002] Diffusion barrier is used to prevent the mutual diffusion of atoms between different materials. Tungsten-titanium film is widely used as diffusion barrier for Al, Cu, and Ag wiring of integrated circuits due to its good thermal stability, corrosion resistance, chemical stability, low electron mobility, and good surface adhesion. It plays a role in hindering metal diffusion and improving the bonding strength between metal film and substrate. At present, magnetron sputtering deposition of thin film is a commonly used method for preparing tungsten-titanium thin film. This method can obtain thin films with good crystallinity and high density. When tungsten-titanium thin film is prepared by magnetron sputtering, the film performance is not only affected by the magnetron sputtering process, but more importantly, it is related to the performance of the magnetron sputtering raw material - tungsten-titanium alloy target. Studies have shown that high-density, high-purity, low-titanium-rich phase β1 (Ti, W), and fine and uniform grains of tungsten-titanium alloy targets are the key factors for obtaining high-performance tungsten-titanium thin films.

[0003] At present, the preparation of tungsten-titanium alloy targets mainly adopts traditional sintering methods such as vacuum hot pressing, hot isostatic pressing, and spark plasma sintering to control the density, purity, and grain size of the target. These methods do not pay attention to the control of the gas content and solid solubility of the target. However, the gas content and solid solubility of the target are also key indicators of high-quality tungsten-titanium alloy targets, affecting the quality of subsequent sputtering coating. At the same time, these preparation methods also have the disadvantages of long heating and cooling time, low yield, high requirements for the professional background of the operator, complex process, and high energy consumption. For this reason, the present invention proposes a preparation method for tungsten-titanium alloy targets, which can ensure the acquisition of tungsten-titanium alloy targets with low gas content, high solid solubility, and fine and uniform grains while obtaining high density and high purity. This method has the advantages of simple operation, short production cycle, and low requirements for operators. Summary of the invention

[0004] In order to solve the problems of high gas content and low solid solubility in the existing tungsten-titanium target materials, the present invention provides a method for preparing a tungsten-titanium alloy target material. The present invention adopts high-energy ball milling powder mixing + cold isostatic pressing + microwave sintering + solid solution treatment to obtain the tungsten-titanium alloy target material. The method can ensure low gas content, high solid solubility and fine and uniform grains while obtaining high-density and high-purity tungsten-titanium alloy target materials. The method has the advantages of simple operation, short production cycle and low requirements on operators, and will provide a new method for preparing target materials for diffusion barrier layers of large-scale integrated circuits. The specific preparation steps of the tungsten-titanium alloy target material are as follows:

[0005] (1) High-purity tungsten powder and titanium powder are subjected to high-energy ball milling to obtain a mixed powder.

[0006] (2) The mixed powder is subjected to cold isostatic pressing to obtain a rough blank.

[0007] (3) The rough blank obtained by cold isostatic pressing is subjected to microwave sintering to obtain an alloy target blank.

[0008] (4) Placing the alloy target material blank in a tubular furnace for solution treatment to obtain a tungsten-titanium alloy target material.

[0009] Preferably, the purity of the tungsten powder raw material is ≥99.999%, and the particle size is ≤5μm; the purity of the titanium powder raw material is ≥99.99%, and the particle size is ≤30μm. The mass percentage of titanium powder in the mixed powder is 10%-30%, and the remainder is tungsten powder.

[0010] Preferably, in step (1), a polytetrafluoroethylene tank is used for high-energy ball milling, the balls used for ball milling are high-purity titanium balls or high-purity tungsten balls, the ball-to-material ratio is 5:1-10:1, the rotation speed is 150-250 r / min, the ball milling mixing time is 5-10 h, and the ball milling gas medium is Ar gas.

[0011] Preferably, in step (2), the cold isostatic pressing conditions are: pressure of 20-40 MPa, and pressing time of 30-60 min.

[0012] Preferably, in the sintering process in step (3), SiC is used as an auxiliary heating material and Al2O3 fiber sheath is used as a thermal insulation material.

[0013] Preferably, in step (3), the process parameters of microwave sintering are: microwave sintering frequency is 2-6 GHz, power is 4-10 kW, sintering atmosphere is H2, heating rate is 20-60°C / min, sintering temperature is 1100-1300°C, and holding time is 20-40 min.

[0014] Preferably, in the step (4), the temperature of the solution treatment in the tubular furnace is 800-1000° C., the time is 3 h-4 h, and the solution treatment gas atmosphere is Ar gas.

[0015] Preferably, after step (4), surface treatment, machining and binding cleaning steps can be performed according to actual needs.

[0016] The tungsten-titanium alloy target material prepared by the present invention is applied in the sputtering process of the diffusion barrier layer of an integrated circuit.

[0017] Beneficial Effects of the Invention

[0018] (1) The present invention uses high-purity titanium balls or high-purity tungsten balls to perform high-energy ball milling on tungsten-titanium powder, thereby avoiding impurities introduced during the mixing process of balls of different materials and ensuring the purity of the tungsten-titanium alloy target. At the same time, the tungsten-titanium mixed powder is subjected to strong impact, grinding and stirring by high-purity titanium balls or tungsten balls to produce mechanical alloying, which can refine the grains, greatly improve the activity of the powder, and improve the uniformity of particle distribution and the bonding between the interface between the reinforcement and the matrix, thereby ensuring the density of the material.

[0019] (2) The present invention adopts low-pressure cold isostatic pressing technology. The low pressure can ensure that the internal gas of the tungsten-titanium rough billet overflows in time during the subsequent microwave sintering process. At the same time, the degree of powder deformation is small, which avoids the abnormal growth of grains during the subsequent microwave sintering process and ensures the low gas content and grain size uniformity of the tungsten-titanium alloy target.

[0020] (3) The present invention adopts microwave sintering + solution treatment preparation technology, which has the advantages of fast heating speed, low sintering temperature, inhibition of grain growth and refinement of material structure, improvement of material performance and safety and pollution-free, etc., which ensures the high density of tungsten-titanium alloy target material, small and uniform grain size and reduces the content of titanium-rich phase. It also has the advantages of low energy consumption and short production cycle.

[0021] (4) The density of the high-density tungsten-titanium alloy target prepared by the present invention is ≥99.5%, and the grain size of the titanium-rich phase and the maximum grain size of the tungsten-rich phase are both smaller than the existing tungsten-titanium alloy industry standards. The maximum grain size of the titanium-rich phase in the tungsten-titanium alloy target prepared by the present invention is ≤50μm, and the maximum grain size of the tungsten-rich phase is ≤10μm. The existing tungsten-titanium alloy industry standards require that the maximum grain size of the titanium-rich phase is ≤120μm, and the maximum grain size of the tungsten-rich phase is ≤15μm.

[0022] (5) The C content of the tungsten-titanium alloy target prepared by the present invention is ≤50ppm, the O content is ≤800ppm, the titanium-rich phase is evenly distributed, and the mass percentage of tungsten in the titanium-rich phase can reach more than 50%.

[0023] (6) Since the tungsten-titanium alloy target prepared by the present invention has a low oxygen content, it is not easy to form oxide particles during the sputtering process, which will not cause film defects and circuit short circuits, and will not cause device failure.

[0024] (7) Since the tungsten-titanium alloy target prepared by the present invention has a low carbon content, it is not easy to form carbides during the sputtering process, which will not affect the electrical properties and durability of the film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a simplified diagram of the preparation process of a tungsten-titanium alloy target material for an integrated circuit diffusion barrier layer. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0027] Example 1

[0028] A tungsten-titanium alloy target material is prepared, and the preparation process is as follows: Figure 1 The specific steps are as follows:

[0029] (1) High-energy ball milling: high-purity tungsten powder and titanium powder are mixed by high-energy ball milling to obtain a mixed powder, wherein the mass percentage of titanium powder in the mixed powder is 10%, and the rest is tungsten powder; the purity of the tungsten powder raw material is 99.999%, and the particle size is 3 μm; the purity of the titanium powder raw material is 99.99%, and the particle size is 25 μm. The high-energy ball milling jar uses a polytetrafluoroethylene jar, the balls used for ball milling are high-purity tungsten balls, the ball-to-material ratio is 10:1, the rotation speed is 200 r / min, the ball milling mixing time is 8 h, and the ball milling gas medium is Ar gas.

[0030] (2) Cold isostatic pressing: The powder obtained by high-energy ball milling is placed in a graphite mold and pressed by low-pressure cold isostatic pressing to obtain a rough blank. The cold isostatic pressing process parameters are: pressure 30 MPa, pressing time 60 min.

[0031] (3) Microwave sintering: The rough blank obtained by cold isostatic pressing was placed in a microwave sintering furnace for sintering. The microwave sintering frequency was 2.45 GHz, the power was 6 kW, the sintering atmosphere was H2, the heating rate was 60 °C / min, the sintering temperature was 1100 °C, and the holding time was 30 min. During the sintering process, SiC was used as an auxiliary heating material and Al2O3 fiber sheath was used as a thermal insulation material.

[0032] (4) Solution treatment: The tungsten-titanium alloy target material obtained by microwave sintering is placed in a tubular furnace for solution treatment. The temperature of the solution treatment in the tubular furnace is 1000°C, the time is 4 hours, and the solution treatment gas atmosphere is Ar gas.

[0033] After the prepared tungsten-titanium alloy target material has completed the above steps, it is subjected to surface treatment, machining, binding and cleaning steps in sequence.

[0034] Example 2

[0035] A preparation method of a tungsten-titanium alloy target material, the specific steps are as follows:

[0036] (1) High-energy ball milling: high-purity tungsten powder and titanium powder are mixed by high-energy ball milling to obtain a mixed powder, wherein the mass percentage of titanium powder in the mixed powder is 10%, and the rest is tungsten powder; the purity of the tungsten powder raw material is ≥99.999%, and the particle size is 5μm; the purity of the titanium powder raw material is ≥99.99%, and the particle size is 25μm. The high-energy ball milling jar uses a polytetrafluoroethylene jar, the balls used for ball milling are high-purity titanium balls, the ball-to-material ratio is 5:1, the rotation speed is 150r / min, the ball milling mixing time is 5h, and the ball milling gas medium is Ar gas.

[0037] (2) Cold isostatic pressing: The powder obtained by high-energy ball milling is placed in a graphite mold and pressed by low-pressure cold isostatic pressing to obtain a rough blank. The cold isostatic pressing process parameters are: pressure 40 MPa, pressing time 30 min.

[0038] (3) Microwave sintering: The rough blank obtained by cold isostatic pressing was placed in a microwave sintering furnace for sintering, wherein the microwave sintering frequency was 2.8 GHz, the power was 10 kW, the sintering atmosphere was H2, the heating rate was 20 °C / min, the sintering temperature was 1200 °C, and the holding time was 40 min. During the sintering process, SiC was used as an auxiliary heating material and Al2O3 fiber sheath was used as a thermal insulation material.

[0039] (4) Solution treatment: The tungsten-titanium alloy target material obtained by microwave sintering is placed in a tubular furnace for solution treatment. The temperature of the solution treatment in the tubular furnace is 800°C, the time is 3 h, and the solution treatment gas atmosphere is Ar gas.

[0040] After the prepared tungsten-titanium alloy target material has completed the above steps, it is subjected to surface treatment, machining, binding and cleaning steps in sequence.

[0041] Example 3

[0042] A preparation method of a tungsten-titanium alloy target material, the specific steps are as follows:

[0043] (1) High-energy ball milling: high-purity tungsten powder and titanium powder are mixed by high-energy ball milling to obtain a mixed powder, wherein the mass percentage of titanium powder in the mixed powder is 10%, and the rest is tungsten powder; the purity of the tungsten powder raw material is ≥99.999%, and the particle size is 3μm; the purity of the titanium powder raw material is ≥99.99%, and the particle size is 10μm. The high-energy ball milling jar uses a polytetrafluoroethylene jar, the balls used for ball milling are high-purity tungsten balls, the ball-to-material ratio is 5:1, the rotation speed is 250r / min, the ball milling mixing time is 10h, and the ball milling gas medium is Ar gas.

[0044] (2) Cold isostatic pressing: The powder obtained by high-energy ball milling is placed in a graphite mold and pressed by low-pressure cold isostatic pressing to obtain a rough blank. The cold isostatic pressing process parameters are: pressure 20 MPa, pressing time 60 min.

[0045] (3) Microwave sintering: The rough blank obtained by cold isostatic pressing was placed in a microwave sintering furnace for sintering. The microwave sintering frequency was 6 GHz, the power was 10 kW, the sintering atmosphere was H2, the heating rate was 20 °C / min, the sintering temperature was 1300 °C, and the holding time was 20 min. During the sintering process, SiC was used as an auxiliary heating material and Al2O3 fiber sheath was used as a thermal insulation material.

[0046] (4) Solution treatment: The tungsten-titanium alloy target material obtained by microwave sintering is placed in a tubular furnace for solution treatment. The temperature of the solution treatment in the tubular furnace is 1000°C, the time is 3 h, and the solution treatment gas atmosphere is Ar gas.

[0047] After the prepared tungsten-titanium alloy target material has completed the above steps, it is subjected to surface treatment, machining, binding and cleaning steps in sequence.

[0048] Comparative Example 1

[0049] For comparison, the difference between this comparative example and Example 1 is that the balls used for ball milling the mixed powder in step (1) are WC cemented carbide balls, and the rest are the same as Example 1.

[0050] Comparative Example 2

[0051] For comparison, the difference between this comparative example and Example 1 is that (2) the cold isostatic pressing pressure is 100 MPa, and the rest is the same as Example 1.

[0052] Comparative Example 3

[0053] For comparison, the difference between this comparative example and Example 1 is that (3) the temperature of microwave sintering is 800° C., and the rest is the same as Example 1.

[0054] Comparative Example 4

[0055] For comparison, the difference between this comparative example and Example 1 is that the step (4) of solid solution treatment is eliminated, and the rest is the same as Example 1.

[0056] Comparative Example 5

[0057] For comparison, the difference between this comparative example and Example 1 is that the high-energy ball milling process in step (1) is replaced by a simple mixing of pure tungsten powder and titanium powder using an ordinary three-dimensional mixer.

[0058] The properties of the alloy targets prepared in various embodiments and comparative examples are shown in Table 1.

[0059] Table 1 Basic parameters of tungsten-titanium alloys prepared in various examples and comparative examples

[0060]

[0061] From the above results, it can be seen that the tungsten-titanium alloy target prepared in Example 1 has a lower carbon content and a higher purity than that in Comparative Example 1. This is mainly because the wear of the WC ball in Comparative Example 1 during the ball milling process causes the carbon and some metal impurities in the material itself to enter the tungsten-titanium mixed powder, resulting in a higher carbon content and lower purity in the prepared tungsten-titanium alloy target.

[0062] The tungsten-titanium alloy target prepared in Example 1 has lower O and C contents than those in Comparative Example 2, and the overall grain size of the target is relatively small and uniform. This is mainly because the rough blank formed by high-pressure cold isostatic pressing in Comparative Example 2 is relatively compact, and the gas cannot be discharged in time during the subsequent sintering process. At the same time, the high-pressure cold isostatic pressing process causes a large deformation of the mixed powder. In the subsequent sintering process, some grains grow abnormally, resulting in an overall uneven grain size.

[0063] The overall comprehensive performance of the tungsten-titanium alloy target prepared in Example 1 is better than that in Comparative Example 3, mainly because the sintering temperature is an important parameter affecting the density of the target material. The microwave sintering temperature in Comparative Example 3 is too low, the degassing effect is poor, and a high solid solubility and dense tungsten-titanium alloy target cannot be formed, resulting in poor sintering effect.

[0064] The tungsten-titanium alloy target prepared in Example 1 has higher titanium-rich phase solubility and density than those in Comparative Example 4, mainly because the solid solution treatment step is reduced in Comparative Example 4, and the conditions for further diffusion of tungsten and titanium elements are lacking compared to Example 1, so the solid solubility of the titanium-rich phase is significantly reduced, which in turn affects the distribution and density of the titanium-rich phase of the tungsten-titanium alloy prepared by sintering.

[0065] The tungsten-titanium alloy target prepared in Example 1 has higher solid solubility and density of the titanium-rich phase than that in Comparative Example 5, and the overall grain size of the target is relatively small and uniform, mainly because the high-energy ball milling process can further refine the powder and the repeated impact of the ball milling during the ball milling process produces a large number of dislocations and distortions inside the grains. The increase of these defects and the reduction of the grain size reduce the diffusion activation energy during the sintering process, resulting in an increase in the diffusion rate, an increase in the solid solubility, and a uniform organization, thereby increasing the density. In Comparative Example 5, a three-dimensional mixer is used to simply mix pure tungsten powder and titanium powder, lacking the process of improving the solid solubility and density by the high-energy ball milling mixing process.

[0066] In summary, the preparation method of the present invention can be used to prepare a tungsten-titanium alloy target material with low gas content, fine and uniform grain size, uniform distribution of titanium-rich phase in tungsten-rich phase, high density and high solid solubility. The prepared tungsten-titanium alloy target material can be used for sputtering of diffusion barrier layers of integrated circuits.

Claims

1. A method for preparing a tungsten-titanium alloy target, characterized in that: The steps include: (1) high-purity tungsten powder and titanium powder are subjected to high-energy ball milling to obtain a mixed powder; (2) cold isostatic pressing the mixed powder to obtain a rough blank; (3) subjecting the rough blank obtained by cold isostatic pressing to microwave sintering to obtain an alloy target blank; (4) Placing the alloy target material blank in a tubular furnace for solution treatment to obtain a tungsten-titanium alloy target material.

2. The method for preparing a tungsten-titanium alloy target according to claim 1, characterized in that: The purity of the tungsten powder raw material is ≥99.999%, and the particle size is ≤5μm; the purity of the titanium powder raw material is ≥99.99%, and the particle size is ≤30μm. The mass percentage of titanium powder in the mixed powder is 10%-30%, and the remainder is tungsten powder.

3. The method for preparing the tungsten-titanium alloy target according to claim 1, characterized in that: In the step (1), a polytetrafluoroethylene tank is used for high-energy ball milling, the balls used for ball milling are high-purity titanium balls or high-purity tungsten balls, the ball-to-material ratio is 5:1-10:1, the rotation speed is 150-250 r / min, the ball milling mixing time is 5-10 h, and the ball milling gas medium is Ar gas.

4. The method for preparing the tungsten-titanium alloy target according to claim 1, characterized in that: In the step (2), the cold isostatic pressing conditions are: pressure of 20-40 MPa, and pressing time of 30-60 min.

5. The method for preparing the tungsten-titanium alloy target according to claim 1, characterized in that: In the step (3), SiC is used as an auxiliary heating material during the sintering process, and the Al2O3 fiber sheath is used as a thermal insulation material.

6. The method for preparing the tungsten-titanium alloy target according to claim 1, characterized in that: In the step (3), the process parameters of microwave sintering are: microwave sintering frequency is 2-6 GHz, power is 4-10 kW, sintering atmosphere is H2, heating rate is 20-60°C / min, sintering temperature is 1100-1300°C, and holding time is 20-40 min.

7. The method for preparing a tungsten-titanium alloy target according to claim 1, characterized in that: In the step (4), the temperature of the solution treatment in the tubular furnace is 800-1000° C., the time is 3 h-4 h, and the solution treatment gas atmosphere is Ar gas.

8. The tungsten-titanium alloy target prepared according to claim 1 is used for sputtering the diffusion barrier layer of an integrated circuit.

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